On Thu, 14 Jul 2011 17:52:25 +0200, Michele Da Rold wrote: > Hello everybody, > I'm new to i2c development some don't kill me if my questions are stupid!! > > I'm using bitbanging i2c driver for an AT91 devices, > the AT91 is master and I have a slave that reply, during a write, with a > NAK after last byte. > The i2c specification permit this solution but i2c linux driver no. Can you please quote the part of the I2C specification which you think says this? I read it differently (page 10 of I2C 2.1 specification, section 7.2: Acknowledge): "Usually, a receiver which has been addressed is obliged to generate an acknowledge after each byte has been received, except when the message starts with a CBUS address." "If a master-receiver is involved in a transfer, it must signal the end of data to the slave-transmitter by not generating an acknowledge on the last byte that was clocked out of the slave. The slave-transmitter must release the data line to allow the master to generate a STOP or repeated START condition." So, a master-receiver must nack the last byte, but a slave-receiver must not. So your slave device is misbehaving - or you are actually trying to write more bytes to it than it can handle. > (i have see the possibility to set the I2C_M_IGNORE_NAK but ignore all > NAK and isn't right!) This should indeed be avoided unless you really have to use it. > There is a solution or I have to modify the code? First ensure that you are sending the right number of bytes to the device, with the correct sequence. If you think you're really doing the right think, get in touch with the vendor of the slave device and ask them why their device misbehaves. -- Jean Delvare -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
